I. Field of Invention
This invention relates generally to a force-sensing probe and related method of operation for probing periodontal tissue, and more specifically to a force-sensing probe with automatically resetting force-sensing and force-indicating means for placing in contact with the tissue at a particular level of force, and for sensing and indicating that level of force.
II. Background Information
A prior art force-sensing probe is illustrated in FIG. 1(A). An object of the probe is to enable a clinician to obtain a standarized depth measurement of a periodontal pocket which surrounds a tooth, and which has a floor of periodontal tissue. The probe senses the level of the force at which the probe is placed in contact with the periodontal tissue at the floor of the pocket, and indicates when that level has reached a predetermined level, enabling a clinician to obtain a standardized depth measurement of the pocket by measuring the depth when that level has reached the predetermined level.
As illustrated in the figure, the prior art probe is comprised of a magnetizable member 1, a movable lever 2 which has a probe tip 3 at one end and which pivots around pivot pin 4, a coil 5 wrapped around magnetizable member 1, a power supply 6, a potentiometer 11, an annunicator 7, and a contact point 10. Power supply 6 is coupled to coil 5 causing a current to flow through the coil and magnetizing magnetizable member 1 to generate a magnetic force and releasably hold movable lever 2 in an "engaged" position. As illustrated, the power supply is also coupled in series to the movable lever, to the annunicator, and to the contact point. Movable lever 2 has a beveled surface 8 at one end, and magnetizable member 1 similarly has a beveled surface 9 at one end which is parallel to and flush with the beveled surface of the movable lever when the lever is in the "engaged" position.
To measure the depth of a periodontal pocket with the prior art probe, a clinician places the probe tip of the probe in contact with the periodontal tissue at the floor of the pocket. The periodontal tissue exerts a particular level of force on the probe tip, and the clinician adjusts the placing of the probe until the level of force exerted is equal to a predetermined level, defined as the level of force required to overcome the magnetic force releasably holding the movable lever in the "engaged" position. When the level of force is equal to the predetermined level and the magnetic force is overcome, the lever is caused to pivot around the pivot point and move to a "disengaged" position. In the "disengaged" position, the lever is placed in contact with contact point 10 thereby activating annunciator 7 which preferably consists of a buzzer, a lamp or the like. When activated, the annunicator visibly or audibly indicates that the level of force is equal to the predetermined level, and that the lever has moved to the "disengaged" position. After the lever has moved to the "disengaged" position, the clinician then reads the depth measurement from a depth measuring scale (not shown) incorporated within the probe and placed near the probe tip.
To enable the clinician to adjust the predetermined level of force required to overcome the magnetic force releasably holding the lever in the "engaged" position, a potentiometer 11 is provided. When the potentiometer is adjusted, the current flowing through coil 5 is altered, and the level of the magnetic force releasably holding lever 2 in the "engaged" position is proportionately changed.
A variant prior art probe is illustrated in FIG. 1(B). As illustrated in the figure, the variant prior art probe comprises a slidable permanent magnet 101 to which is attached a cylinder 102 of nonmagnetic material with an extended bore 103 for receiving the threaded end of a stub shaft 104. The opposite end of the stub shaft is attached to knob 105. When the knob is turned in a clockwise direction, the threaded end of the stub shaft is caused to progress within the extended bore thereby sliding the cylinder and the permanent magnet to which the cylinder is attached towards the knob across mountings 106.
The variant prior art probe further comprises a magnetizable member 107 which is fixed to a probe housing 108 by means of mountings 109, a movable lever 110 which pivots around pivot pin 111, a probe tip 112 attached to one end of the movable lever, and a battery 113 which is coupled in series to the movable lever. The battery is further coupled in series to an annunicator 115, and to a contact point 114.
Similarly to the prior art probe illustrated in FIG. 1(A), the movable lever is releasably held in an "engaged" position by a magnetic force exerted by the magnetizable member, and a predetermined level of force is required at the probe tip to overcome the magnetic force. The level of the magnetic force releasably holding the lever in the "engaged" position and hence the predetermined level of force required at the probe tip to overcome the magnetic force proportionately increases as the knob is moved in a counter-clockwise direction causing the slidable magnet to move closer to the magnetizable member. When the level of force at the probe tip is equal to the predetermined level, the lever is caused to pivot to a "disengaged" position, and contact the contact point thereby activating the annunciator. When activated, the annunciator visibly or audibly indicates that the level of force at the probe tip is equal to the predetermined level, and that the lever has moved to the "disengaged" position.
The prior art and variant prior art probes suffer from the disadvantage that the movable levers of such probes must be manually reset from the "disengaged" position to the "engaged" position after each measurement of pocket depth. Since a clinician must make an average of six measurements per tooth, such manual resetting is inefficient.
Another disadvantage is that such probes do not provide a clinician with a precise indication of the level of force at the probe tips of such probes when a depth measurement is taken, making the standardization of that measurement difficult. Instead, such probes only provide the clinician with an indication that the level of force is equal to or greater than the predetermined level, but do not indicate the extent to which the predetermined level is exceeded.
Accordingly, it is an object of the present invention to provide a force-sensing probe for obtaining standardized pocket depth measurements while the force exerted on the probe by the periodontal tissue at the floor of the pockets is equal to a predetermined level which, for each pocket depth measurement, senses and indicates the level of force exerted on the probe by the periodontal tissue at the floor of the pocket while the measurement is taken, and which then automatically resets in preparation for another measurement.